1. Field of the Invention
The present invention pertains to the field of position sensing devices, particularly to rotational position sensing devices for measuring the rotation of a shaft and arm assembly typically used for doors of transit vehicles such as buses and trains.
2. Description of Related Art
Rotational position sensing devices for measuring the rotation of a shaft and arm assembly used for transit vehicle doors are known in the art. Such devices are used in situations where it is desirable to properly determine the position (i.e., open, closed, partially open, or a particular angle) of a vehicle door operating with a shaft and arm assembly.
Transit vehicle doors supporting a shaft and arm assembly may include, but are not limited to, slide-glide doors, plug doors, swing doors and bi-fold doors as are known in the art. Further, it may be desirable to fasten position sensing devices to shaft and arm assemblies used in other contexts (i.e., for doors or other devices utilizing a rotatable shaft) to measure or otherwise determine the axial rotation of a shaft relative to a fixed structure.
In many cases, measuring the rotational position of a shaft of a shaft and arm assembly requires a position sensor (i.e., a potentiometer, rotary encoder, or other like device) to be fixed to the shaft and arm assembly of a door. One method of fixing a position sensor to a shaft and arm assembly involves securing the shaft portion of the sensor to the shaft and arm assembly and securing the housing portion of the sensor with a fastener mounted to the structure (i.e., the vehicle, door, wall or other structure). The disadvantage of this method is that any non-height adjustments of the shaft and arm assembly relative to the structure will require readjustment of the position sensor.
Another method known in the art to fix a position sensor to a shaft and arm assembly of a vehicle door requires fixing the position sensor directly to the adjuster shaft of the shaft and arm assembly. However, if such a method is employed with a traditional position sensing device, the position sensor will require readjustment every time the height of the shaft and arm assembly is adjusted.